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capsule

Small recoverable, but not reusable, vehicle for carrying animals, equipment or humans in space.

capture

Process by which a celestial object or artificial satellite passing within the vicinity of a star is pulled into orbit by gravitational attraction. The object is thus captured into orbit or falls to the surface of the star.

ceiling

Altitude at which a balloon stays aloft when buoyancy balances its weight.

centrifuge

Large rotating machine often used in training to subject astronauts to a centrifugal force much stronger than the Earth’s gravity, similar to what they will experience during launch and reentry.

chemical propusion

Mode of jet propulsion that uses energy generated by a chemical reaction. The propulsive agent is produced by the chemical transformation of propellants.

circular orbit

Orbit of constant radius. In practice, a circular orbit is in fact an orbit with a very low eccentricity.What is an orbit?

combined test

Environmental test that subjects equipment to at least two types of environmental conditions at the same time.

comet

A class of small celestial objects in the Solar System consisting of a frozen, rocky nucleus, which vaporizes on approaching the Sun, producing an envelope of dust and gas, and a “hairy” tail up to several million kilometres long.

composite

Part of a spacecraft comprising several autonomous interconnected elements that are designed to separate. A launch vehicle has an upper composite and a lower composite.

conduction

Transfer of heat energy within a body or between bodies through colliding particles without any apparent movement of matter.

constellation

Applied to satellites, a set of artificial satellites performing the same continuous functions and spaced in such a way to fulfil a common mission. A constellation may comprise non-synchronous satellites in low-Earth or medium-Earth orbit, designed for example to carry out telecommunications or satellite navigation missions.

convection

Transfer of heat energy by movement of a fluid. For example, convection takes place when heating water in a saucepan.

One of three theoretical minimum spacecraft velocities determined by Russian scientist Konstantin Tsiolkovsky.

1. Earth orbital velocity The velocity that theoretically must be imparted to a body launched from the Earth’s surface to cause it to go into orbit around the planet. It is about 7.9 km per second.

2. Earth escape velocity The minimum velocity that is sufficient for a body to escape from Earth’s gravitational attraction. It is about 11.2 km per second.

3. Solar System escape velocity The minimum velocity that is sufficient for a body to escape from the Sun’s gravitational attraction. It is about 16.6 km per second for a spacecraft launched from Earth. One of three theoretical minimum spacecraft velocities determined by Russian scientist Konstantin Tsiolkovsky.

cosmonaut

Russian equivalent of an astronaut.

cryogenic

Term describing low-temperature phenomena, techniques and properties, often below the boiling point of oxygen (–183°C. Also applied to mechanisms that use cryogenic processes (for example, the cryogenic stage of a launch vehicle) or substances produced or stored at low temperature.

cryogenics

Science and techniques involved in the production and application of low-temperature phenomena.

cryosphere

All of the land surface layers made up of ice and snow : icecaps, ice fields or icebergs, glaciers, snow-covered lands.